Laminator equipment is used to apply to one or both sides of a printed circuit board a resistive layer using a dry process. For the same purpose, wet photoresist material is applied. The circuit board consists of polyester material as carrier. The attached photoresist layer is generally designated here as film. The film has a protective layer and is stored on a supply reel, and after the protective layer is pulled off, the film features a sticky underside. After cutting of the film with a cutting fixture, the film is pressed onto (laminated) the printed circuit board in the presence of pressure and heat using heated laminating rollers.
It is particularly important that the cut overlay for the printed circuit board be accurately and cleanly cut and applied, and especially that the film overlay be cut slightly shorter than the printed circuit board. By this method, otherwise considerable consumption of material is saved and a protruding sticky rim of cut film on the printed circuit board is avoided.
In the course of further work with a board having a rim of this kind, following boards may stick together or the border of the film layer may crumble off. Because of the sticky nature of the debris, it is to be expected that operational interruptions may occur with this type of machinery. Because these debris particles are very sticky, it must be expected that they will reach the boards, disturb the subsequent photo-illumination process, and damage the conductor trace paths. Consequently, the film is always cut shorter than the plate. This also results in financial saving of expensive film.
A laminator for cut-sheet lamination of the described kind is already known, especially with cutting the film shorter than the printed circuit board. In that device for laminating, the film is positioned at the front edge of the printed circuit board, and both are led through the overlay rollers together with the printed circuit boards using swiveling feed rollers which guide the film in and stretch the film using positioning devices.
In that laminating device, the cutting device moves against the direction of the film transport upwards and cuts the film somewhat shorter than the printed circuit board. A disadvantage is that a relatively complicated construction with many failure-prone parts is needed resulting also in high fabrication costs. A further disadvantage of that version is that transport of the film and movement of the printed circuit board are stopped as the film is cut from the plate which results in the disadvantage that, with heated overlay rollers, the rollers come to rest against the printed circuit boards which have film already applied, resulting in local overheating of the film in the region of the overlay rollers.